Energy Resources and Impacts

Transcription

1 Chapter 23 Energy Resources and Impacts No Clicker Registered Anderson, R. Backus, N. Bardi, S. Berliner, L. Dalugdug, J.-M. Fisher, J-R. Jie-A-Fa, R. Henesey, N. Ichikawa, D. Johnson, Brett Kim, D. Linton, R. Montague, W. Rempel, C. Ruger, P. Smith, R. Stahlman, A. What is Energy? Energy is work (a force acting through a distance). Energy is heat (the amount of heat required to raise 1g of water 1ºC). E = mc 2 (in nuclear reactions mass can be converted to energy). Energy is a valuable commodity. Units of Energy Joule 1 kg m 2 / s 2 (mv 2 ) = 1 w/s. KWH = 3.6 x 10 6 joule (3.6 million j) Calorie (the amount of heat required to raise 1g of water 1ºC) (= 4.18 j). Food Calorie = 1000 cal BTU (the amount of heat required to raise 1 pound of water 1ºF). Quad = BTU Renewable Solar Direct Photo-voltaic Thermal (Mirror focusing) Wind Biomass Hydroelectric Geothermal Non-Renewable Nuclear (U-fission) Nuclear (Fusion) Fossil Fuels Oil Natural Gas Coal Oil Shale & Tar Sand 1

2 Solar Direct Solar-Thermal: Mirrors focus sunlight to boil water. Photo-Voltaic Cells: Direct conversion to electricity. Indirect Wind Hydro-electric Biomass: Wood, grain, sugar, trash. Solar Direct Solar-Thermal: Mirrors focus sunlight to boil water. Photo-Voltaic Cells: Direct conversion to electricity. Indirect Wind Hydro-electric Biomass: Wood, grain, sugar, trash. Geothermal Energy from Earth s Internal Heat Engine Geysers, CA Supplies San Francisco. New Zealand, Iceland Hot Dry Rock Fossil Fuels: Energy from the ancient sun Coal Oil Natural Gas Oil Shale and Tar Sand Reserves and Resources Reserves are the known amount of a mineral in the ground that is exploitable with current technology and under current economic conditions. Resource includes the reserves plus estimated undiscovered deposits. 2

3 Origin of Fossil Fuels Plants store energy from the sun by photosynthesis. CO 2 + 2H 2 O = CH 4 + 2O 2 If biomass is buried before re-oxidation. the reduced carbon is preserved as fossil fuels. Burial and compaction separates solid (coal), liquid (oil) and gaseous (gas) fractions. Oil and Gas Liquid and gas fractions are mobile and can be trapped by impermeable layers. Only in sedimentary rock. Most deposits of Paleozoic and Mesozoic origin. ( my) Search is to look for natural traps. Oil Shale and Tar Sand Oil Shale is immature kerogen deposit. Tertiary age (Green River Formation) Tar Sand is over-mature kerogen Oil Shale and Tar Sand Reserves nearly equal total of oil and gas Colorado and Utah have large deposits of oil shale in Tertiary rocks. Alberta, Canada has large deposits of tar sands. Coal Lignite (Peat) Sub-bituminous coal Bituminous coal Anthracite (Metamorphic) 3

4 Coal Reserves are very large (~10 times that of oil and gas). Exploitation may depend on technology to scrub CO 2. Scrub CO 2? But what do you do with it? Liquefy CO 2 and put on ocean bottom. Pump it down gas wells? Tie it up in stable minerals? Mg 2 SiO 4 + 2CO 2 = 2MgCO 3 + SiO 2 olivine + carbon dioxide = magnesite + quartz Use Solar Energy and engineered microbes to turn CO 2 back into fuel Bio-engineering CO 2? Design microbes for C fixation in soils or in ocean bottom. Design microbes that can photosynthesize CO 2 to make fuel plus oxygen. Cap and trade can catalyze new approaches Methane Natural gas is mostly methane. Methane is a greenhouse gas. Methane is CH 4. CH 4 + 2O 2 = CO 2 + 2H 2 O Burning methane produces ~40% less CO 2 per joule of energy than coal. Coal-bed Methane Coals beds form and release methane. Producing methane from coal beds started increasing about 20 years ago. Coal bed methane gave about 10% increase in gas reserves in US Shale Methane Shale forms form clay sediments in shallow marine environments. Shale can capture organic sediments and contain methane. New horizontal drilling and hydrofracture technology. Natural gas reserves in US have increased by 40% in past 5 years. 4

5 Shale Methane Shale is ~ 70% of sedimentary rock. Shale methane could increase world reserves of gas by 40 to 150%. Hydrofracture technology (fracking) has some potential environmental problems such as ground-water contamination and minor earthquakes. Methane Hydrates Methane (CH 4 ) forms an ice-like compound with water at oceanbottom P&T. It is an energy resource larger than known natural gas reserves. Will require new technology for extraction. Methane Hydrates: Ice that burns Methane Hydrates: Energy source and hazard Clicker Question: A greenhouse gas is one that: A. absorbs UV, but passes visible and IR B. absorbs visible but passes UV and IR. C. absorbs IR, but passes UV and Visible D. will burn (oxidize) in the air. E. has a green color like Cl2 Greenhouse Gases CO 2, CH 4 Pass Visible light Opaque to Infra red Earth captures energy from sun but cannot re-emit Causes warming 5

6 Carbon Dioxide Colorless, odorless, tasteless, poisonous gas Animal life cannot exist in >1% CO 2 Plants love it. Current level is about ppm. Increases at about 1% per year. Greenhouse gas. 6

7 Nuclear U fission 235 U is less than 1% of natural Uranium. Can be enriched to 3.3%. US light-water reactors use water as moderator and coolant. Produces about ~16% of US electricity and about 7% of total energy consumed. No new reactors. Size of energy resource is larger than coal. Clicker Question: Nuclear power emits almost zero greenhouse gas A. True B. False 235 U Fission US light-water reactor Water is moderator Moderator slows neutrons for capture. Fuel is UO 2 enriched to 3.3% 235 U (or MOX) Fuel produces 3 million times as much energy per gram as fossil fuel. 235 U Nuclear- Other Canadian (Deuterium moderated) High Temperature Gas-Cooled Graphite moderated Highly enriched fuel Chernobyl & Fort St. Vrain Thorium Radioactive Waste About half of 235 U is consumed. Spent fuel rods contain 90 Sr and 137 Cs plus trans-uranics (Np, Pu, Am, Cm, etc). Cs and Sr have 30 year half-lives. TUs have up to 24,000 year half lives. Spent fuel still produces ~900 W/Ton of power after 10 years. Geologic Host Rocks Salt (Germany, France, WIPP) High Thermal conductivity Self-sealing (flows plastically) Granite (Sweden) Good thermal conductivity Stable craton environment Tuff (Yucca Mountain, Nevada) It s in Nevada. It s already contaminated. 7

8 Yucca Mountain Yucca Mountain Yucca Mountain Recent Volcanism Recent Volcanism Recent Volcanism: Problem Obvious problem 8

9 Future Technologies Breeder (Convert 238 U to Pu) 238 U is 99%+ of natural U Early attempts were unstable. MOX fuels (use weapons Pu) Fusion Nuclear fusion of light elements H, He, Li Near break-even point (as always). Size of resource is inexhaustibly large. Renewable Solar (Big thermo-nuclear reactor in the sky) Direct Photo-voltaic (house-hold scale) Mirror focusing (power-plant scale) Wind (transmission lines) Biomass Hydroelectric Geothermal Clicker Question: The US should Increase investments in: A. Nuclear power plants B. Solar thermal power plants C. Wind turbines D. B and C above E. All of the above Clicker Question: The best choice would be: A. Nuclear power plants B. Solar thermal power plants C. Wind turbines D. Distributed solar (photo-voltaic) E. Geothermal power plants Mineral and Water Resources: Conservation and Recycling Mineral Resources: Metals Precious Metals Au, Ag, Pt Chalcophile Metals Cu, Zn, Pb Iron Lithophile Metals Mg, Al, Si, Ti, Li, REE 9

10 Mineral Resources: Metals Precious Metals Au, Ag, Pt Pt is used in catalytic converters Price =~1.25 x Au (~$1600) Mineral Resources: Metals Chalcophile Metals Cu, Zn Recycling has reduced demand. Emerging economies will need more. Mineral Resources: Non-Metals Aggregate: Sand & gravel Limestone (cement) Salt, Phosphate, Sulfur Water Resources How much are you willing to pay for water? $1.25 / liter? ($200 / shower?) Water Resources 70% of planet s surface is ocean. Desalination is expensive. Water Resources Per capita water consumption in US has decreased by ~ 20% in past 25 years. (better pipes) 10